Timber Cantilever Beam Underslung From Header

[bnjneer]

For aesthetic purposes, the architect is proposing a cantilever timber beam that is placed under the header so that the bottom of the cantilever member will line up with the ceiling inside so that it looks like the ceiling extends indoors to the outdoors (the header spans a large window opening and sliding door opening). The header is potentially a glulam beam. Trusses are used to frame the roof/ceiling on the interior and the cantilever member sits below the header (approximate dimensions...24" deep trusses supported by 13.5" deep glulam header, and the 2x8 cantilever member is hung below the header. The cantilever back span will be supported by some means.) My question...I would like to use a "belt and suspenders" type of connection between the header and the cantilever member at the header location. I am thinking of preferably using a saddle type connection that hangs over the header and sits under the cantilever member for positive connection, but I can't find a product that fits this need. Any suggestions?

I have other ideas, but would appreciate hearing other's ideas.

By the way, I am a bridge engineer, and I am using a residential structural engineer to design this for me, but I want to know what options are out there to make sure I am not proposing something too conservative.

Thank you.

 

[BAretired]

How about underslung beam hangers?

https://www.google.ca/search?q=unde...cOKjAKIj4GgBw&ved=0CAkQ_AUoAQ&biw=546&bih=323

BA

 

[dhengr]

Bnjneer:
A framing plan/sketch and section would help show the relative elevations of the various parts and their framing relationship. Show dimensions, sizes, etc. What are the loads? 2x cantilevers which penetrate an exterior wall are notoriously difficult to flash and keep water tight. I think BA has the right idea, but you probably want to block laterally btwn. the 2x cantilevers. Look in USP’s or Simpson’s catalogs for this type of hardware.

 

[bnjneer]

BA:
This is close to the right idea, but the 2x8 cantilever beam needs to pass completely under the 13.5" header, and I am not able to find a hanger that has enough depth to support the 2x8 and wrap up and over the header. If I get a chance, later today I will post a sketch for further clarification.

Thank you

 

[structSU10]

what a about using a post cap as a hanger?
Link
A lot of simpson post caps have uplift load capacities noted - it may just require a call to see if they feel comfortable with them in sustained tension.

 

[EngineeringEric]

Simpson Twist Straps? or a really deep hanger... Simpson THA426-2 is 26" long, so 7.25"+13.5" < 26" you can even use a THAC on one side and a THA on the other side for belt/suspender type fun.

 

[nac521]

Keep in mind the uplift load values on Simpson straps are increased for duration (wind/seismic) so you would have to adjust accordingly. Depending on the loads I would use some sort of a twist strap for small reaction then onto LGT2, VGT, CC, or CCQ as the loads increase. And if those done work, a custom made connector. Anything is possible, depends on how much the client is willing to spend.

 

[msquared48]

How dowes the Architect propose to brace the bottom flange of the cantilever at the header to prevent rollover?

Mike McCann
MMC Engineering

 

[a2mfk]

I think something like this would give you lateral bracing like MSQUARED indicated.

http://www.strongtie.com/products/c...PU-HW-HWU_GLULAM.asp?source=glulamcat#gallery

Depths up to 30" were listed in their tables.

 

[msquared48]

a2mflk:

That will not work considering the 2.75" of the vertical metal plate that would have to be cut into the top of the cantilever, cutting the tension flange.

There has to be another way here, without that vertical plate. Perhaps a double saddle hanger arrangement?

As an alternative, I think I would also try to use a vertical rod and bearing plates with a wider cantilever beam, with some means of lateral bracing that would be acceptable architecturally, yet functional.

The more I think about it, a double saddle hanger arrangement would work very well here. May have to specially design it though - not off the shelf for 2X material.

Mike McCann
MMC Engineering

 

[BAretired]

Maybe a double saddle, one over the header and one under the cantilever, connected with four all-thread rods?

BA

 

[bnjneer]

All good ideas folks. Thank you.

I've attached a quick sketch so you all understand the detail (I've not shown the connection, though).

If you have other good ideas, please let me know, along with good ideas for blocking.

Thank you!

 

[jayrod12]

I think that is prime for the upside down post cap idea. or twist straps.

 

[a2mfk]

Mike, maybe my coffee isn't kicking in yet, but I don't follow. I attached a sketch, maybe I am missing something?

 

[msquared48]

a2mfk:

Thanks for the sketch. I see it now. You are right and I was envisioning something else. I need coffee...

Mike McCann
MMC Engineering